The Ponseti method, developed by Ignacio Ponseti in the 1940's, has been a long-standing treatment for clubfoot, a paediatric foot deformity. Clubfoot sees an infant's foot turned inward, sometimes so severely that the bottom of the foot faces sideways or even upward, which can lead to pain or long-term disability.
'The Ponseti method of manipulation of clubfoot has revolutionised clubfoot treatment in the world over the last 20 years,' says Chris Lavy, Professor of Orthopaedic and Tropical Surgery and Consultant Orthopaedic and Spine Surgeon at NDORMS. 'This paper helps explain the science behind tendon stretching.'
The Ponseti technique corrects the deformity by gradually stretching and casting the foot several times until it reaches its correct position. Each time the foot is manipulated a little further causing the tendons to stress then relax, a process known as stress relaxation. The Ponseti technique has been well studied but there was one area that was left unexplained. The long-term impact of the stress relaxation of the tendon extracellular matrix (ECM) was unknown so the research team was looking at how the tendon reacted and whether it was damaged after being forced into a strain for days.
Using three different methods to study the effect of stress relaxation on tendon ECM, the team illustrated the mechanism of tissue lengthening behind the treatment. They found that a long-term stress relaxation successfully lengthened a tendon and that elasticity recovered.
'We found a treatment time dependency in both tendon lengthening and ECM changes,' said Mu-Huan Lee, DPhil candidate at Oxford's Department of Materials. 'We showed that the changes to the tendon happen faster than anticipated so in future the Ponseti method could potentially be improved by shortening the intervals between casting.'
The study was funded by the National Institute for Health Research (NIHR) and Oxford Biomedical Research Centre (BRC).